Kettle, contactor, or other batch processes are usually used to make lithium complex greases from a fatty acid such as 12-hydroxy stearic acid and a complexing agent such as a smaller chain diacid. Complex greases manufactured by these processes can exhibit good structural stability, as measured by Two-Hour Room Temperature Shell Roll Stability (ASTM D1831), 10,000 or 100,000 stroke worked penetration (ASTM D217), and Penetration Split (60 stroke worked penetration minus unworked penetration).
While several simple lithium greases have been made by a continuous in-line grease process, a review of the literature only found one type of lithium complex grease made by this method. Wittse, et al. in U.S. Pat. No. 4,444,669 describes an example of this type of lithium complex grease by a continuous in-line grease process with azelaic acid or dimethyl azelate complexing agents. However, Wittse's lithium complex grease exhibits poor structural stability, efficiency, 10,000 stroke penetration, and penetration split.
It would be desirable to be able to make a lithium complex grease in a continuous in-line process that exhibits good structural stability because a continuous in-line process can be more economical than batch type processes. Experience has shown however that the current flash chamber used in simple lithium grease in-line processes do not support sufficiently rapid removal of volatile by-products formed in the process when using diacids and dialkl ether complexing agents needed from lithium complex greases due to excessive foaming of the grease in the flash chamber.
An object of the present invention therefore is to provide a method for making a lithium complex grease having a penetration split (60X-UW) of within −20 mm/10 to +10 mm/10, a roll stability (D1831) of <30 mm/10, and a dropping point (D2265) of >240° C. in a continuous in-line process.
Another object is to provide an improved flash chamber suitable for rapid removal of volatile constituents from viscous materials such as grease.
These and other objects of the invention will become apparent from a reading of the description which follows.